Process of purifying naphtha stocks



Patented Mar. 21, 1933 "DAVID E. DAY, DE LOS PATENI. F -mg:

CALIFORNIA rnocnss orrunrrvme narnm s'rocxs Application filed December5,1931.v s ria1@iw6.f 579,as7,.

This application is a'continuation in art of my application Serial No.370,325, led June 12, 1929, for method of purifymg petroleum oils. j

a This invention relates to an improved method for purifying hydrocarbonoils derived by distillation or cracking ofgmineral oils or mineraloilproducts, such as lubrieating oil stodks, lamp oil distillates, gaso- 1oline or naphtha stocks, or any other distill,-

ates produced in generalrefinery practice, and more specifically refersto the treatment of gasoline or naphtha'stocks produced by crackingpetroleum oils or distillates derived from relatively high sulphurbearing crude petroleum oils, in which hydrogen sulphide, mercaptans andother sulphur bearing conipounds, as well as varying percentages; ofphenols and unsaturated hydrocarbons (such ,,-.29 as Idiolefines and'acetylenes) may be present or formedduring a distillation or crackingoperation. v ,1 For the purpose, of simplifying the.description-oftheinvention, reference will be 5 made to gasoline ornaphtha stocks mainly.

By well known methods, gasoline stocks derived from cracking petroleumoils or from distilling high sulphur bearing crude petroleum oils areusually purified by varying .39 treatments with sulphuric acid, followedby neutralization with a water solution of-analkali, a sweeteningoperation and a final distillation. In the sweetening operationhypochlorite of soda or sodium plumbite in a 5 water solution of causticsoda may be employed to convert corrosive sulphur'compounds intononcorrosive bodies, so'that the treated gasoline stock will be sweet tothe doctor test.

In these treatments, particularly where hypochlorite of soda isemployed, chlorinated hydrocarbons may be formed to a small extent,which may be converted into corro sive compounds during a subsequentdistillation. Also all the sulphur bearing hydrocarbons remaining in thegasoline stock after the purification operation form corrosive acidcompounds during combustion, and if in appreciable amounts, mayattackthe metal parts of anengine, Therefore, it is advantageous in theJpurificationbfgasoline or naphtha stocks "to" use a purif in agentwhich in it's'elfwillnot'formchlorinated oils, and one'which reinovecertain percentage of "the sulphur compoundsffiom a ga e: lineqrnaphthaistok and 'pelymefiz the nus'cable hydrocarbons sothatmagma-may be p te t erafiem ye l bse en i i l m- Y1. i 9 Y I .,my' pedin .aprl et s l N 370,325, filedfl June 12, 1929, forfmethod'of Pi i ie pe -c am s 1s," .h e closed that hydrocarbon oils, such as gasoline ornaphtha stocks, maybe purified by passing the same, commingled with asubstantially concentrated: water solution of caustic soda, causticpotash sodiumfcarbonate or potassium carbonate," 'throu'gh a heatingcoil Leade 5 P e sur l fii int o- P nt ,0 'stant vaporizatiom atatemperature be tween 350 and fioO-ldegrees F.,thenreleas- *ing thepressure andseparating by distillation and fractionation 'ap'urifiedgasoline or naphthafrom the excess'caustic alkali, the 7 extractedimpurities and the products of polymerization or condensation. Water iscontinuously or intermittently introduced into the lower section of thedistillation and fractionating apparatus in quantities sufii- 30 'cienttoreplace the vaporized water-from the caustic alkali solution, so as tomaintain the used caustic alkali or carbonate and products of reactionin a fluid state.

Now I have discovered an improvement thereto, in which I have determinedthat, it is an advantage to mix air with the gasoline or naphtha stockduringjthe treating operation, in quantities sufiicient to oxidize thecorrosive sulphur compounds contained 9 therein into compounds that maybe extracted to a certain extent with the caustic alkali or carbonatetreating solution; also that the introduction of air into the gasolineor naphtha stock assists in the polymerization of the unstablehydrocarbons and thereby produces gasoline or naphtha which is lower insulphur content, sweet to the doctor test,'and contains substantially nogums or gum forming constituents. The air may be mixed with the 7 9sweet to the doctor test.

liminary treatment with sulphurio'acidpr' other agents topartlyipurif-y'the'isame,-=or may be first partly purif ed by myinvention and the purification completed by-methods known in the art. Inthe case pf asoline or naphtha stocks produced by'cra'c mg high sulphur;bea ring crude petroleum oils. or -residuums, it may be advantageous totreat such gasolineor naphtha stocks with sulphuric acid ;at. lowtemperatures, ranging froinap- PE QlM- Q to -3 d e ees ib rektreatment-with I the concentrated water, solu tio c cei tie lk l m sabenate s il eeedg ape s and pe t-e; we n e One of he princlpal objectsof this invent is o a ompl sh p rti lde rhu i tio'n andfpurificationbfgasoline'or naphtha stocks produced by thermo-niolecular decompositionof'high boilingtpetrole im 'Qils, by--a treatment with ais bstntianyconcentrated water solution .of [an alkali hydroxide ,or car.-bonate and air, underapressuresufiicient' to prevent substantialvaporiaatio n of; the gasoline or naphtha stock, and atja)temperaturefof approximately 350-501) degrees 'F. follQYifd 35 by adistillation and fractionat n operation to separate-"the products 'fo'freaction higher, boiling polymerized product from purified gasoline ornaphtha. so

- Another object of the invention is to wide a continuous, rapid andeconomieal proc- .ess for-purifying gasoline'o'r naphtha stocks bytreating the same, under superatmospheric pressure sufficient tomaintain the gasoline or naphtha stock in a liquid phase, with asubstantially concentrated water solution of an alkali hydroxide orcarbonate and air, at

temperatures of approximately 350-500 degrees F., to polymerize,substantially all the unstable hydrocarbons contained therein, and atthe same time remove oxygenated hydrocarbons and render the gasoline ornaphtha Another object of the invention is to provide a continuous andeconomical method for improving the color-and removing gums and gumforming hydrocarbons from gasoline or naphtha stocks, so that the samemaybe kept in storage for relatively long periods of time without changein color or quality by the formation of polymerized bodies. y

Other objects and advantages will be apparent from' the preferredembodiment of this invention, which will now be more fully explained byreference to the accompanying drawing, which is a diagrammatical repre-'tha or other petroleum oil stocks to be processed. Pipe 1, controlled byvalve 2, connects gasoline stockgtank 3 near the top to a sourceof'supply not shown. Pipe 4, controlled by valve 5, connects gasolinestock tank 3 to the inlet side of -pump'6. Pipe 7 connects pump 6 to jetmixer 8.

13represents generally a caustic soda tank for holding a concentratedsolution of a caustic alkali' such' as" caustic soda or caustic potash.Pipe let, controlled by valve 15, connects caustic soda 'ta-nk.13 nearthetop to a source of supply not ,shown.' Pipe 11, controlled by Valve12, connects caustic soda tank 13 near the bottom to the inlet side of85 pump-110.. Pipe9connects the dischargeside of pump 10to jet mi'xer'8. Pipe 10,0011- trolled by yalveel, 'islc onnected to jet mixer sandleads to a source of'compressed air. f

Pipe 16 connects jet'inixer 8 to heater coil 38. Heatercoil 38 isstationed'in furnace 17. Furnace 17 is providedwith a burner 18, whichleads to a supply of fuel oil not shown.

Pipe 39','.controlledby pressure release valve 19, connects'heater coil.38 to distillation. tower 20. Pipe42, controlled by valve 43, connectspipe 39 to a source of compressed air. Distillation tower '20 isprovided with bubble trays 21.: Pipe 22, controlled by valve 23,connjects distillation tower 20 near the bbttQmi'iO a source'of water orsteam supply not shown. Pipe 25, controlled by valve 24, connectsdistillation tower 20 at the bottom to tank 26. Pipe 28, controlled byvalve 27, connects tank'26 to a storage not shown.

I :Pipe 29 connects distillation tower '20 at the top to condenser coil31. Condenser coil '31 is stationed in condenser box 30, and .isprovided with a water inlet pipe 32 and a water outlet pipe 37. Pipe 32leads to a ,1

46' near the top to an absorber not shown. -115 Pipe 33' connects airseparator 46 to treated gasoline tank 34. Pipe 36, controlled by valve35, connects treated gasoline tank 34 near thebottom to a storage notshown.

The preferred process as carried out in the apparatus just described isas follows:

Petroleum oil distillate, such as gasoline orv naphtha stock, containedin tank 3, is permitted to flow through pipe 4 and into the inletside ofpump 6, the rate of flow being.

governed by operation of valve 5. Pump 6 continuously discharges thegasoline stock through pipe 7 under a pressure of approximately 1501000pounds gauge, into jet mixer 8, wherein the gasoline stock iscontinuously 'commingled' with the necessary quantity of air, and asubstantially concentrated water solution of caustic alkali coming fromthe caustic soda supply tank 13.

The air introduced into jet mixer 8 comes from a source of compressedair through pipe 40, controlled by valve 41, and may range fromapproximately one-half volume to four volumes of air per volume ofliquid gasoline under treatment.

The water solution of caustic alkali contamed in supply tank 13 ispermitted to flow through pipe 11 and into the inlet side of pump 10,which discharges the same, under a pressure ranging from approximately150- T000 pounds gauge, through pipe 9 and into jet mixer 8, the rate offlow being governed by operation of valve 12. The quantity of watersolution of caustic alkali employed may range from as low asapproximately 1 per cent to as high as 10 per cent by volume or more,depending upon the stock to be treated. For example, if a crude gasolinestock contains a high percentage of impurities to be extracted, or hashad a preliminary treatment with sulphuric acid, as much as 10 per centby volume or more of a concentrated water solution of caustic alkali maybe employed.

The pressure maintained on the system by means of pumps 6 and 10 isregulated so that the commingled mixture of water solution of causticalkali and gasoline or naphtha stock under treatment will be maintainedin a substantially liquid phase, such pressure depending upon theboiling points of the gasoline or naphtha stock and the temperatureemployed.

From jet mixer 8 the gasoline stock, commingled with the water solutionof caustic alkali and air, passes through pipe 16, heater coil 38, pipe39, pressure release valve 19 where the pressure is reduced toatmospheric or approximately atmospheric, and into distillation tower20. The c-ommingled mixture passing through heater coil 38 is heated toa temperature greater than 350 degrees F. Preferably, approximately 400degrees F. is a suitable temperature to employ in treating ordinarygasoline or naphtha stocks. how ever, with some grades of petroleumdistilla-tes as high as 500 degrees F. or a little higher may beemployed.

In distill tion. tower 20 the purified. gasoline stock, at a temperatureof approximately 400 degrees F., together with a portion of the watercontent of the alkali solution, is vaporized and separated from. theproducts of reaction and the caustic alkali employed. The purifiedgasoline stock. mixed with water vapor and air, passes out ofdistillation tower 20, through pipe 29, into condenser coil 31, which isstationed in condenser box 30, wherein the major portion of the purifiedgasoline stock and water vapor is condensed to a liquid 22d passedthrough pipe 47 into air separator FFrom -"separator 46 "the: tr ma.gasoline {passes througb pipe" ;33 into tank 34: i From treatedgfaspli-netank 34 the purified gasoline stpck may i b'e conducted -to astorage" not shown throughj pipe'..36; controlled by valv'e -35. l hepurified ga soline stoek sow'obtained may :bei therea'ftes treated; di-necessary, by othefi m'ethods known 'inj, the f art} or may: beslibjeeteil to a distillation operation to sepahate ffractions havinganydesired 1 ange sof boilifig"p'0ints: w .ei-v' 'ra'g no l."-"""(i Thecaustic alkali-'and 'products of reaction,

separate in the bottom" of distillation twefi 20 are intermittently or=continuously withdrawnintogtaiik 26 through pipe 25; controlled; byyalye 24, water being: continuously or intermittentlyiintroducedinto'the lower section of 'dist'illati'on tower 20 through pipe "22,'controlledbytyalve 23', inquantities sufli- --cient to-replace thevaporizedwater from the caustie'alkali iwater solution, so astomaininthe used cau'stiwalkali and products of reactionin'a fiuidcondition. Pf?

' From tank: 26-:the-excess ;water solution of 4 v 1 caustic alkali aindpr )'ducts of reaction iare "conducted to a": storage: not shown through"pipe 28f-controll'ed' by valve 27," and the canstic alkali may beseparatedfrom the reaction products and recovered for reuse: I

Pi a The air in the treatment may be intro- ;duced'into the treatingsystem through pipe 42, controlled by'rva'lve43, which is connectedtop'pe' 39, and'leads to a source of compressed ='air-not shown'w While*the'pro'cess' her ein 'de'scribed is well adapted for carryinggout theobjectsof this "inventiong'various modifications'and':changes may: 1 be{'made', such= asthe employment of 'various" types of .fraction'atingequipment 3 known in: the;artto' effect any desired separationot "thetreated gasoline I stockinto frac tionshaving a 'desired range-ofboiling points, .and the "invention includes'all such changes andmodifications as appear within the scope M of the appended claims.

I claim:

1. A process of purifying naphtha stocks, comprising, commingling anaphtha stock with a substantially concentrated water solution of acaustic alkali, passing the commingled mixture through a heating zone attemperatures of approximately 350500 degrees F., under a pressuresuflicient to prevent substantial vaporization of the naphtha stock,releasing the pressure and introducing air into the oommingled :mixtame,and .a purified naphtha iby vaporization, fractionatiw (condensationfrom produots of reaction, excess caustic alkali and .aeriform products.

2. A.- process of removing gum forming emstituents from crackedgasolinestock, comprising, contacting the cracked gasoline stockwithawater-solution of aeanstiealkall, at temperatures-of approximately3-50-5Q0degrees R, under a pressure sufiicient to prevent substantialvaporization thereof, while passing through a heating zone, for a periodof time 'snfiicienttocause unstable hydrocarbons eontainedjin thegasoline stock-to polymerize with the formation of gums, then reducingthe pressure to-approximately atmospheric, intnoduemg air,- andseparating by vaporization, fractionation and condensation purifiedgasoline stookinom reaction and polymerization products, excess caustica1- .kali and aeriformzpnodncts,

3.. A continuous pnooess for purifying gasoline stocks derived bythermo-molecular decomposition of higher boiling petroleum oils,comprising, continuously comm'ingling a gasoline stock with amatersolution-of a caustic alkali; continuously passing the commingledmixture through a heatnlg zone to heat the eommingled gasoline stock andwafer solu tion of caustic alkali to a temperature of approximately 400degrees'R, undera pressure sufiicient to prevent substantialvaporization therein; continuously releasing the prwsure after thecommingled .mixtune. of gasoline stock and water solution of causticalkali has passed'through the said heating zone and has been heated to atemperature of approximately 400 degrees F.;icontinuously introducingair into the heated mixture of gasolinestock and water solution ofalkali; continuously passing the same into a vaporizing zone andvaporizing, fractionating, condensing and separating purified gasolinestock mixed with water from higher boiling products of reaction, excesscaustic alkali and aeriform' products; continuously introducing water"into the said vaporizing zone in quantities suificient to replace waterof vaporization; and continuously withdrawing products of reaction andintroduced water containing caustic alkali, substantially as described.

In testimony whereof I afiix my signature.

DAVID E. DAY.

